found a service manual for a 505b and the picture does not show a shroud but it does have a fan on the heatsink. See the picture below. it looks to me like that bottom fan in your picture should have been on the heatsink at one point.

found a service manual for a 505b and the picture does not show a shroud but it does have a fan on the heatsink. See the picture below. it looks to me like that bottom fan in your picture should have been on the heatsink at one point.

found a service manual for a 505b and the picture does not show a shroud but it does have a fan on the heatsink. See the picture below. it looks to me like that bottom fan in your picture should have been on the heatsink at one point.

What i thought :-) whoop right for once

That will be the fan that is flapping around in the bottom left of the OP's post